Thermal stability, chimeric

Yoshida, H., Kojima, K., Witarto, A. B., and Sode, K. (1999). Engineering a chimeric pyrroloquinoline quinone glucose dehydrogenase improvement of EDTA tolerance, thermal stability and substrate specificity. Protein Eng., 12, 63-70. 

There are two reports describing the use of nucleosides with other sugar conformations. A method for preparing internally P-labelled l-DNA has been described using T4 polynucleotide kinase. Chimeric DNA composed of tandem a- and p-anomeric strands have been used in TFOs and shown to have enhanced thermal stability compared to all a- or p-anomeric oligonucleotides. ... 

The chimeric genes obtained were used to transform E. coli cells, with each single clone expressing one variant of PQQ-glucose dehydrogenase. The enzyme was isolated and assayed in a buffer containing PQQ to form the holoenzyme, and a colorimetric indicator. Enzymatic activity was assayed for different substrates, and the effect of EDTA and thermal stability were investigated. When... 

Improved Thermal Stability in Chimeric Enzymes. 6-Glucosidase from C. gilvus is optimally active at 35°C, whereas that of A. tumefaciens exhibit maximum activity at 60°C. With regards to heat stability, 6-glucosidase from C. gilvus shows complete activity up to 30°C, retains about 80% of its maximum activity at 35°C, and inactivates completely at 55°C. On the other hand, A. tumefaciens enzyme is stable up to 55°C and even at 65 C, it retains 60% of its maximum activity. 

In chimeric isopropylmalate dehydrogenase from an extreme thermophile, Thermus thermophile, and a mesophile. Bacillus subtilis, the stability of each chimeric enzyme was also proportional to the content of the amino acid sequence from the T. thermophile enzyme (26). The thermal stability of the chimeras was also intermediate between that of the highly labile Type II hexokinase and the relatively stable Type I isozyme (57). 

When the substrate of solble burchwood xylan is used, chimeric xylanase displayed an optimum pH of 6.2 at 50 C, and it was stable in the pH range S.O-11.0 at 70 X. Fig. 3 shows the temperature optimum and thermal stability profiles of chimeric and die parental em e. XynB-CBM2b displayed the identical temperature activity profile as that of XynB a temperature optimum at 90 C and stability up to 90 °C. These results indicate that fUsion of the CBM2b to XynB has no effect on die structure and function of die catalytic domain. 

Figure 5. Thermal stability of the chimeric and parental xylanases. , XynA O, XynB , Apnc A, APnc.

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